Today we’re releasing a feature to help you discover if your site serves undesirable "soft” or “crypto” 404s. A "soft 404" occurs when a webserver responds with a 200 OK HTTP response code for a page that doesn't exist rather than the appropriate 404 Not Found. Soft 404s can limit a site's crawl coverage by search engines because these duplicate URLs may be crawled instead of pages with unique content.

The web is infinite, but the time search engines spend crawling your site is limited. Properly reporting non-existent pages with a 404 or 410 response code can improve the crawl coverage of your site’s best content. Additionally, soft 404s can potentially be confusing for your site's visitors as described in our past blog post, Farewell to Soft 404s.

You can find the new soft 404s reporting feature under the Crawl errors section in Webmaster Tools.

Here’s a list of steps to correct soft 404s to help both Google and your users:

Confirm that you’ve configured the proper HTTP Response by using Fetch as Googlebot in Webmaster Tools

If you now return 404s, you may want to customize your 404 page to aid your users. Our custom 404 widget can help.

We hope that you’re now better enabled to find and correct soft 404s on your site. If you have feedback or questions about the new "soft 404s" reporting feature or any other Webmaster Tools feature, please share your thoughts with us in the Webmaster Help Forum.